A sensor network includes spatially distributed autonomous sensing devices to monitor physical or environmental conditions, (such as temperature, humidity, pressure, movement, etc.) and to record data about the physical events to deliver the data through the network to a user's location. In some networks the communication channels between the user and the sensing devices are bi-directional, also enabling control of the sensing devices. Today such networks are used in many industrial and consumer applications, such as industrial process monitoring and control, machine health monitoring, transport of goods etc.